1. Field of the Invention
The present invention relates to a process of manufacturing a crystalline silicon solar cell, and more particularly, to a process which not only offers the simplified chemical process with minimal problems about dealing with follow-up chemical solutions, but also achieves the improvement on the photoelectric conversion efficiency of the crystalline silicon solar cell, without adding any extra processing steps to the existing standard process of manufacturing the crystalline silicon solar cell.
2. Description of Related Art
The sun is the source of all energy on Earth. Most of currently known energies such as oil, coal, natural gas, water power, solar energy, wind power, photosynthesis energy, and ocean energy are directly or indirectly from the sun. The energy (˜5×1020 J) generated by irradiating the sunlight over the entire Earth's surface for one hour is enough for the whole human being to use about 1 year. It is estimated the sun continues emitting sunlight at least five billion years or more, so that the solar energy is regarded as unexhausted, free clean energy.
After the Industrial Revolution, the rapid growth of the global population, the development of the civilization, the improvement of relative technology, and demand for high living quality result in increasingly high demand for and dependence on the energy. Large-scale use of fossil fuels leads to significant decrease in global storage capacity and rise in prices. Large amount of pollutant emission causes global warming and climate anomalies, and other issues about posing threats to human living environment as well. Soaring in the prices of fossil fuels including oil and gas has drawn attention to the global emphasis on alternative energy. It greatly effluences the countries such as Taiwan which heavily relies on imported energy, up to 98% of what is needed. The average CO2 emission for traditional energy generation is about 530 t/GWh. Even though the solar energy is comparatively environmentally friendly, it still generates CO2 emission of 5 t/GWh.
The currently standard process of manufacturing a crystalline silicon solar cell includes the following nine steps:
(1) wafer inspecting, surface defect etching, and cleaning;
(2) textured;
(3) phosphorus diffusing;
(4) phosphosilicate glass etching;
(5) laser isolation;
(6) anti-reflection film coating;
(7) screen printing (silver and aluminum glum);
(8) connector sintering;
(9) solar cell testing and detecting.
Among the above steps, step (1), (2), (3) and (4) are wet-chemical processes which need to use organic acidic and alkali chemicals such as hydrochloric acid (HCl), nitric acid (HNO3), hydrofluoric acid (HF) and isopropyl alcohol (IPA). Those chemicals produce large amount of organic acidic and alkali gas and liquid waste, resulting in the burden on the environment. Therefore, the currently available solar cells cannot be regarded as green products.
The inventors have made long-term efforts in solving such a problem, and successfully got an approach to achieve a process of manufacturing a crystalline silicon solar cell, which can overcome the problem encountered in the prior art.